Cigarettes and other products of tobacco manufacture are, for the most part, blends of two principal types of tobacco, so-called "flue-cured" and "burley" tobaccos. American cigarettes, for example, are generally comprised of two-thirds flue-cured tobacco and one-third burley tobacco.
For the most part, the cultivation of flue-cured and burley tobaccos occurs in the states of North Carolina, Virginia, Kentucky, Tennessee, South Carolina and Georgia. Production of flue-cured tobacco is largely in a region adjacent to the Atlantic Coast whereas burley tobacco is grown in more inland and upland regions. The growing and harvesting of flue-cured tobacco and burley tobacco differ in a number of respects.
In the case of flue-cured tobacco, the lowermost leaves are detached from the plant stalk as they mature and begin to yellow. The detached leaves are suspended in bunches on sticks which are hung in barns and the tobacco "flue-cured," i.e., dried by air heated by heat exchange with hot air passing through flues.
Burley tobacco, on the other hand, is allowed to mature until nearly all of the leaves on the stalks have yellowed. Then the entire plant is cut off near the ground and the stalk and leaves allowed to wilt in the field over a period of several days. The entire plant is then hung in specially designed barns where it is allowed to air-dry in a slow curing process.
The cultivation of tobacco, particularly flue-cured tobacco, is a labor-intensive process. Therefore, there has been the inevitable trend towards mechanization of this process. To that end, the United States Department of Agriculture has developed a process known as the "homogenized leaf-curing process," which is less expensive than the conventional curing processes.
In this process, the yellowed leaves of tobacco plants grown in the conventional manner are harvested and pulped. Water is added to the pulp which is then agitated at a temperature of about 25.degree. C. for about 24 hours. During this time, the proteolytic enzymes already in the leaves digest some of the proteins that remain in the leaves at the time they are harvested. After the digestion, the excess water is squeezed out of the now dark-brown pulp, which is then dried and serves as a starting material for a reconstituted tobacco product used as a tobacco filler in cigarette manufacture much like the low-quality tobacco obtained as a product of conventional curing processes.
The resulting product is somewhat safer for smoking than tobacco obtained from conventional curing processes since it has a diminished protein concentration, proteins being one source of the undesirable products in cigarette smoke.
As in conventional cultivation, it is of the utmost importance that the tobacco leaves be allowed to turn yellow in the natural way before they are harvested for use in the homogenized leaf-curing process. Nevertheless, the homogenized curing process is not capable of removing sufficient green pigment material from the leaves to the extent that the product has been acceptable to the tobacco industry.
In the course of the slow-burning characteristic of tobacco products such as cigarettes, pipe tobacco and cigars, nicotine, "tars," and other products considered to have adverse effects on the smoker's health are liberated in the smoke which is drawn into the smoker's mouth and lungs. In view of health considerations, cigarette manufacturers have devised systems to reduce the nicotine and tar content of the burning tobacco. However, the biggest part of this reduction has not been achieved by developing new kinds of tobacco low in tar and nicotine. Instead, it has been achieved by changing the manner in which the cigarette is constructed.
Thus, filters that reduce some of the tar content have become widely used. However, most of the reduction has come from so-called "bypass" systems which utilize porous paper in the manufacture of cigarettes which permit air to be drawn through pores in the paper to dilute the gases generated by burning tobacco.
Although these techniques have resulted in a safer smoking product, they do not remove all of the undesirable constituents in the tobacco smoke. Furthermore, these processes result in a reduction in the flavor components of the smoke and this reduction in taste has been criticized by smokers. Accordingly, there exists a need for the development of a tobacco product which is inherently low in nicotine and tars but that retains important flavor ingredients.
Accordingly, an object of the present invention is a tobacco product suitable for use in cigarettes and other tobacco manufactures which has a reduced protein, nicotine and tar content but which retains desirable flavor constituents.
Another object of this invention is to make available a process for obtaining a tobacco product suitable for use in cigarettes and other smoking products which is less labor-intensive than conventional processes.
That these and other objects may be accomplished by the present invention will be apparent to those skilled in the art from the following summary and detailed description of the invention.